Method and device for testing and diagnosing an automotive air conditioning system

ABSTRACT

Test and diagnosis of an automotive air conditioning system ( 2 ) is performed by a device which comprises: temperature-sensing means ( 3 ) for sensing the ambient temperature, pressure-sensing means ( 4, 5 ) for sensing the high and low side pressures of the system ( 2 ), data-storage means ( 62 ) for storing at least one set of reference values of refrigerant pressures and ambient temperatures and at least one set of malfunction diagnosis, a data processor ( 63 ) for comparing said sensed values of ambient temperature and refrigerant pressures with said stored reference values and for associating to each tern of sensed values at least one diagnosis, which is displayed on a display unit ( 7 ), an input unit ( 8 ) and an hand-heldable housing ( 10 ) for containing said sensing and data-storage means ( 3 - 5, 62 ), said data processor ( 63 ) and said display and input units ( 7, 8 ).

[0001] The present invention relates to a method and a device fortesting and diagnosing an automotive air conditioning system.

[0002] From U.S. Pat. Nos. 4,755,957 and 4,967,567 methods and apparatusfor servicing an automobile air conditioning system are already known inwhich electronic processing means including a microprocessor areprovided for initially diagnosing the system.

[0003] It is an object of the present invention to provide an improvedmethod and device for an effective, quick and simple test and diagnosisof an automotive air conditioning system. It is a further object of thepresent invention to provide a method for testing and diagnosing airconditioning system wherein it is considered only the type ofrefrigerant and whether the system has a compressor with fixed orvariable capacity, irrespective of type of automobile and/or systemmanufacturer.

[0004] It is another object of the present invention to provide ahand-holdable, self-contained, light-weight device which allows anyoperator to carry out efficient test and diagnosis of automotive airconditioning systems.

[0005] The above and other objects of the present inventions areaccomplished by means of the method and device defined in theindependent claims. Advantageous embodiments of the invention aredefined in the dependent claims.

[0006] The invention will be now described by way of example and withreference to the accompanying drawings in which:

[0007]FIG. 1 schematically illustrates an air conditioning system with atesting and diagnosing device according to the invention;

[0008]FIG. 2 is a plan view of a preferred embodiment of thehand-holdable housing of the device;

[0009]FIG. 3 is a front view of the housing of FIG. 2.

[0010] Referring to FIG. 1, there is shown a testing and diagnosingdevice 1 according to the invention connected to a typical automotiveair conditioning system 2. The system includes a compressor 20, acondenser 21, a filter 22, an expansion valve 23 and an evaporator 24.

[0011] For purposes of charging and servicing, the system is usuallyprovided with a pair of valve nipples (not shown) at the low 25 and high26 pressure sides respectively.

[0012] The testing and diagnosing device 1 comprises:

[0013] an ambient temperature trasducer 3;

[0014] a low side pressure trasducer 4;

[0015] a high side pressure trasducer 5;

[0016] an analog to digital converting unit 61 for converting the analogoutputs of the trasducers to digital signals;

[0017] a memory 62;

[0018] a digital signal processor 63 connected to the unit 61 and to thememory 62;

[0019] a display unit 7;

[0020] an input unit 8.

[0021] In a preferred embodiment (shown in FIG. 1) the device alsocomprises an I/O interface 64, preferably of type RS232, for connectionwith an external device such as printer or a personal computer.Advantageously all the above mentioned components of the device 1 arecontained in a housing 10 described below in greater detail.

[0022] The device 1 can be provided with external trasducers (not shown)for sensing the refrigerant temperature before and after the evaporator24. A further external trasducer (not shown) can be provided for sensingthe temperature at an air outlet of the conditioning system.

[0023] In the memory 62 are stored reference values of refrigerantpressures and ambient temperature for each kind of refrigerant(generally R-32 or R-134a) and a set of diagnosis with related checkingor repair instructions. Preferably two set of diagnosis are provided,for air conditioning systems having a compressor with fixed or variablecapacity respectively.

[0024] The digital signal processor 63 is arranged to compare the inputdata from the pressure trasducers 4, 5 and the temperature trasducer 3with the values stored in the memory 62 and to associate to each tern ofsensed values (ambient temperature, high and low pressures) at least adiagnosis, which is displayed on the display unit 7. The measured valuesare also displayed for testing purposes. Where the type of refrigerantor compressor is to be selected, this is done through the input unit 8.The digital signal processor 63 is also arranged to verify the operationof the trasducers 3-5.

[0025] Referring now to FIGS. 2 and 3, there is shown a hand-heldablehousing 10 for housing the components of the testing and diagnosingdevice. In a preferred embodiments (shown in FIGS. 2 and 3) the housing10 is formed in two parts, a base 10 a and a cover 10 b, and is providedwith nipples 11, 12 for connecting the pressure trasducers 4, 5 to thelow 25 and high 26 pressure sides of the system via hoses 13, 14 (seeFIG. 1).

[0026] Close to the temperature trasducer 3, an opening 15 is providedin the housing for proper ambient temperature sensing. A further opening16 is provided for connecting a low voltage connector 17 to a lowvoltage source (f.i. the car battery). A still further opening (notshown) is provided for connection with the I/O interface 64.

[0027] The cover 10 b of the housing 10 is provided with the display 70of the display unit 7 and with a plurality of input keys 80-83 of theinput unit 8 (typically ON/OFF, RESET, ENTER, FORWARD).

[0028] The housing 10 can be made of plastic and, as it is clearly shownin FIGS. 2 and 3, has a practical hand-heldable form. Furthermore adevice according to the present invention is light-weight and can beused by unexperienced operator.

1. Method for testing and diagnosing an automotive air conditioning system (2) comprising: providing means (3) for sensing the ambient temperature; providing means (4, 5) for sensing the high and low side pressures of the system (2); providing data-storage means (62) for storing at least one set of reference values of refrigerant pressures and ambient temperatures and at least one set of malfunction diagnosis; providing a data processor (63) for comparing said sensed values of ambient temperature and refrigerant pressures with said stored reference values and for associating to each tern of sensed values at least one diagnosis, which is displayed on a display unit (7); providing an hand-heldable housing (10) for containing said sensing and data-storage means (3-5, 62), said data processor (63) and said display unit (7).
 2. Method according to claim 1 wherein one set of reference values is stored for each type of refrigerant and two set of diagnosis are stored, for air conditioning systems having a compressor with fixed or variable capacity respectively.
 3. Device for testing and diagnosing an automotive air conditioning system (2) comprising: temperature-sensing means (3) for sensing the ambient temperature; pressure-sensing means (4, 5) for sensing the high and low side pressures of the system (2); data-storage means (62) for storing at least one set of reference values of refrigerant pressures and ambient temperatures and at least one set of malfunction diagnosis; a data processor (63) for comparing said sensed values of ambient temperature and refrigerant pressures with said stored reference values and for associating to each tern of sensed values at least one diagnosis, which is displayed on a display unit (7); an hand-heldable housing (10) for containing said sensing and data-storage means (3-5, 62), said data processor (63) and said display unit (7).
 4. Device according to claim 3 further comprising an input unit (8).
 5. Device according to claim 4 further comprising an I/O interface (64) for connection with an external device.
 6. Device according to claim 3 wherein said housing 10 is formed in two parts, a base (10 a) and a cover (10 b), and is provided with nipples (11, 12) for connecting said pressure sensing means (4, 5) to the low (25) and high (26) pressure sides of the system via hoses (13, 14).
 7. Device according to claim 6 wherein, close to said temperature-sensing means (3), an opening (15) is provided in the housing (10) for proper ambient temperature sensing. 